Flexible sheath assembly for an indwelling catheter

ABSTRACT

A flexible sheath assembly for an indwelling catheter is provided which maintains the sterility of an otherwise exposed portion of an indwelling catheter so that the depth of insertion of the catheter within a body may be adjusted without causing contamination. The assembly includes a transparent flexible sheathing which is sealingly secured at its ends to front and rear hubs each having a passageway therethrough which is sized to permit passage of a catheter. The flexible sheathing is longitudinally expandable from a collapsed position wherein the sheathing is twisted about an axis substantially parallel to the length of the sheath. The flexible sheathing in the collapsed position defines a central passageway which is aligned with the front and rear hub passageways for permitting the catheter to be guided through the interior of the flexible sheathing as it is passed between the front and rear hubs. The central passageway is heat set in the flexible sheathing by placing the flexible sheath on a mandrel in its contracted position and heating the flexible sheath in an oven.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related generally to the field of sterilitydevices for catheters and, more specifically, to flexible sheath devicesfor protecting the sterility of the exposed portions of indwellingcatheters.

2. Description of the Prior Art

It is frequently desirable to adjust the depth of insertion of anindwelling catheter which has already been left indwelling for anextended period of time. One example of such a situation occurs when aballoon-tipped catheter inserted within the heart to measure certainheart activities becomes somehow later dislodged. This may necessitatefurther insertion of the catheter in order to properly relocate theheart activity sensor. In such situations it is of utmost importancethat the sterility of the exposed catheter portion be maintained.

The problem of protecting the sterility of exposed portions of anindwelling catheter has been long and well known in the medical art.Thus, prior art includes several patented device which protect sterilityof the exposed portion of an indwelling catheter. An early example, U.S.Pat. No. 3,867,937 to Schwartz, discloses a protective sheath comprisinga very thin plastic tubular member which is in a loose sliding fit onthe outer diameter of the catheter forward of the rear hub end thereof.The protective sheath collapses as the catheter is inserted to a desiredbody depth, with the forward end of the sheath contacting the skinadjacent the entrance site. While the device offers the advantages of avery simple construction, it lacks an airtight seal at the forward endof the sheath. Thus, this device inherently does not prevent thecatheter portion residing within the sheath from becoming contaminatedby outside bacteria entering through the unsealed area between thecatheter and the forward end of the sheath or from bacteria which may bepresent at the skin entrance site.

Two very recent patent references discloses catheter sheath deviceswhich are intended to provide a totally enclosed or sealed environmentalong a length of the exposed portion of an indwelling catheter, thuspermitting later adjustment of the depth of insertion without creatingan unacceptable risk of infection. U.S. Pat. No. 4,327,723 toFrankenhouser discloses a shield assembly including front and rear hubssized to permit movement of the catheter therethrough, a feed tube forconnecting the front and rear hubs, and a flexible sheath connecting thefront and rear hubs. The front hub is connected to the rear portion of ahollow introducer which serves to facilitate the introduction of thecatheter into the body. With this device, a relatively long and rigidinner feed tube is necessary to guide the catheter through the flexiblesheath portion of the assembly. The feed tube serves no further use oncethe catheter is introduced into the body. U.S. Pat. No. 4,327,735 toHampson discloses a device similar to the flexible sheath assemblydisclosed by Frankenhouser except that the feed tube is adapted to beremoved from the assembly once it has served the purpose of guiding thecatheter through the interior of the flexible sheath.

The present invention discloses a flexible sheath assembly which affordsall of the advantages of a totally sealed catheter sheath assembly, asdisclosed in the Frankenhouser and Hampson reference, but further havinga more simplified construction which eliminates the need for arelatively rigid feed tube within the flexible sheath.

Other reference which may have some relevance are:

    ______________________________________                                        U.S. Pat. No.       Inventor                                                  ______________________________________                                        4,250,881           Smith                                                     4,235,232           Spaven et al.                                             4,160,450           Doherty                                                   4,079,738           Dunn                                                      4,037,600           Poncy                                                     3,991,762           Radford                                                   3,894,540           Bonner                                                    3,825,001           Bennet                                                    3,709,223           Macalalad et al.                                          3,474,786           Spademan                                                  3,335,723           Waldman                                                   3,185,151           Czorny                                                    3,010,453           Doherty                                                   2,937,643           Elliot                                                    4,062,363           Bonner                                                    4,029,099           Fifield                                                   3,902,500           Dryden                                                    3,648,704           Jackson                                                   3,792,703           Moorhead                                                  3,854,483           Powers                                                    3,898,993           Taniguchi                                                 4,006,743           Kowarski                                                  4,000,739           Stevens                                                   ______________________________________                                    

Accordingly, it is an object of the present invention to provide animproved flexible catheter sheath assembly for an indwelling catheter.

This and other objects of and advantages of the present invention willbecome more apparent in the following figures and detailed description.

SUMMARY OF THE INVENTION

One embodiment of the present invention is characterized by a flexiblesheath assembly for an indwelling catheter. The assembly includes afront and a rear hub each having a passageway therethrough which issized to permit passage of the catheter. The assembly further includes aflexible sheathing which is sealingly secured to the front and rearhubs. The flexible sheathing is capable of being longitudinally expandedfrom a collapsed position wherein the flexible sheathing is twistedabout an axis substantially parallel to the direction of longitudinalexpansion of the flexible sheathing. In the collapsed position theflexible sheathing defines a central passageway aligned with the frontand rear hub passageways for receiving the catheter therethrough. In thelongitudinally expanded position the flexible sheath assembly maintainsthe sterility of an otherwise exposed portion of the catheter, therebypermitting the depth of catheter insertion within the body to beadjusted after the catheter has been left indwelling for extendedperiods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view partially in section showing theflexible sheath assembly of the present invention in its longitudinallyexpanded position disposed over a catheter and attached to a catheterintroducer.

FIG. 2 is a longitudinal sectional view showing the flexible sheathassembly of the present invention in its collapsed position.

FIG. 3 is a side elevation of a curing fixture for manufacture of thesleeve.

FIG. 4 is a fragmentary top plan view of the curing fixture of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

Referring now to the drawings, the flexible sheath assembly of thepresent invention is generally designated at 10. Sheath assembly 10includes front hub 11 and rear hub assembly 12 which are interconnectedby a transparent flexible sheathing 13. Flexible sheathing 13 extendsbetween front hub 11 and rear hub assembly 12 and is sealingly securedthereto by O-rings 15 and 16, respectively. Front hub 11 and rear hubassembly 12 have respective passageways 17 and 18 therethrough whichpermit the passage of catheter 20. Catheter 20 and introducer 21 are ofconventional construction and those skilled in the art will readilyrecognize that no further description thereof is necessary.

Front hub 11 includes a socket portion 28 which is coupled over thedistal end of introducer 21. Front hub 11 is made from a deformableplastic or rubber material which permits front hub 11 to be sealinglycoupled with introducer 21. Rear hub assembly 12 includes hub 23 and cap24 which are interconnected by coupling member 25, which is externallythreaded at both ends for coupling with the internally threaded portionsof hub 23 and 24. A gasket 26 is fitted between cap 24 and couplingmember 25 and extends partially within passageway 18 thereby serving toseal the space between rear hub assembly 12 and catheter 20 whilepermitting catheter 20 to be freely passed through rear hub assembly 12.While gasket 26 may be made of any suitable material, it has been foundthat a silicone rubber gasket is acceptable for this purpose.

It should be noted that the construction of rear hub assembly 12 may beconsiderably varied without departing from the scope and spirit of theinvention. For example, hub 23, cap 24 and coupling member 25 mayalternatively be one integrally formed part, it being understood thatmeans be provided in rear hub assembly 12 for sealing the space betweenit and catheter 20 while allowing catheter 20 to be passed easilythrough rear hub assembly 12.

It is to be understood that sheath assembly 10 is in its collapsedposition as depicted in FIG. 2 until such time as catheter 20 has beensuccessfully passed through the sheath assembly. In the collapsedposition sheathing 13 of sheath assembly 10 is completely contractedalong axis 29 into a series of tightly packed and twisted folds. Sheathassembly 10 is preferably provided to the physician in its collapsedposition prepackaged in a kit with catheter 20 and introducer 21. Inorder for sheath assembly 10 to maintain its collapsed position so thatcatheter 20 may be easily and quickly passed therethrough to perform acatheterization, the flexible sheathing 13 is packed tightly and twistedon and about the axis of a mandrel 35 upon which the sheath assembly 10is received through front hub 11. The entire sheath assembly 10, mandreland fixture 36 is then placed inside an oven and heated for the purposeof causing the flexible sheathing to take a set. In one preferredembodiment of the invention the flexible sheathing 13 was made of 0.003inch thickness polyethylene plastic sleeving. Such flexible sheathing 13properly sets after being baked for a period of approximately 45 minutesat a temperature of approximately 190 degrees F. After such baking thecuring fixture 36 is removed from the oven and allowed to cool to roomtemperature for 15 minutes before removing the sterility sleeve from themandrel.

It is to be noted that even though this process provides a rigidifyingset causing sheath assembly 10 to maintain its collapsed position priorto use, the flexible sheathing 13 can later be easily longitudinallyexpanded so as to shield an otherwise exposed length of catheter 20.When thus formed, the tightly packed and twisted folds of flexiblesheathing 13 define a central passageway 36 which is in the shape of theexternal surface of the mandrel and aligned with hub passageways 17 and18. Preferably, this central passageway will be cylindrically shapedwith a diameter slightly larger than that of catheter 20, but smallerthan the corresponding diameter of passageway 17 at the interior end 31thereof. The set in the flexible sheathing 13 in the collapsed portionresiliently maintains the size, shape and straightness of the centralpassageway 36. This permits catheter 20 to be easily guided throughsheathing 13 to within passageway 17 of front hub 11, thus ensuring easypassage of catheter 20 through the entire sheath assembly 10.

It may thus be readily appreciated that the present invention discloseda catheter assembly which completely seals an otherwise exposed portionof an indwelling catheter. The invention has the advantages of a simpleconstruction and method of manufacture thus offering cost savings whilealso making the assembly simple to use.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

I claim:
 1. A catheter assembly comprising:a catheter; a catheterintroducer; and a flexible sheath assembly including front and rear hubseach having a passageway therethrough, said hub passageways sized topermit passage of said catheter therethrough, and a flexible sheathsealingly secured to said front and rear hubs and capable oflongitudinally expanding from a collapsed position wherein said sheathforms a series of tightly packed folds contracted on an axis parallel tothe length of said catheter, said sheath in its collapsed positiondefining a central passageway aligned with said front and rear hubpassageways for receiving and guiding said catheter through said sheathduring assembling of said catheter assembly, said flexible sheath havinga rigidifying set biasing it into said collapsed position.
 2. Theassembly of claim 1 wherein said flexible sheath in its first positionis twisted about said axis and said central passageway is cylindricallyshaped.
 3. The assembly of claim 2 wherein said rear hub includessealing means for sealingly attaching said rear hub to said catheter. 4.The assembly of claim 3 wherein said flexible sheath is transparent andis made from a plastic material and wherein said front hub includesmeans for sealingly attaching said front hub to a catheter introducer.5. A flexible sheath assembly for an indwelling catheter,comprising:front and rear hubs each having a passageway therethroughsized to permit movement therethrough of said catheter; flexiblesheathing having first and second ends; a first O-ring sealinglyconnecting said first end of said flexible sheathing to said front hub;and a second O-ring sealingly connecting said second end of saidflexible sheathing to said rear hub, said flexible sheathing beingcapable of longitudinally expanding from a first position wherein saidsheathing is twisted about an axis substantially parallel to the lengthof said sheathing, said sheathing in its first position being contractedalong said axis and defining a central passageway aligned with saidfront and rear hub passageways for directly receiving therethrough saidcatheter, said flexible sheathing having a rigidifying set biasing itinto said first position.
 6. A method of making a flexible sheath for acatheter which includes:attaching hubs to the opposite ends of flexiblesheathing; placing the hubs and flexible sheathing on a mandrel with thehubs close to one another and said sheathing contracted on the mandreland the mandrel extending between the hubs and defining a centralpassageway between the hubs; and causing the flexible sheathing to takea sufficient set in said contracted position so that a catheter can beinserted through said central passageway while said sheathing maintainssaid contracted position.
 7. The method of claim 6 wherein said mandrelis cylindrical and said set is accomplished by heat.
 8. The method ofclaim 7 wherein said flexible sheathing is polyethylene plastic and saidheat is placed on said sheathing for 45 minutes at approximately 190degrees.